Collagen is the major structural protein in the body and one that plays an important role in such diverse biological functions as differentiation, remodeling, wound repair, and aging. Human skin fibroblasts in culture devote a large portion of their protein synthetic capacity to collagen, thus providing a convenient system for studying regulation of collagen synthesis. Our ongoing studies are concerned with regulation of the expression of collagen genes as well as the collagen-specific enzymes prolyl hydroxylase and lysyl hydroxylase, especially with respect to ascorbic acid, an inducer of collagen synthesis, and minoxidil, a drug that we have recently found to specifically inhibit the synthesis of lysyl hydroxylase. We propose studies designed to understand the mechanism of these effects at the molecular level.